Which fireplaces don't need a chimney?
The options
- Electric fireplaces. Plug-in or hardwired units with a flame effect and often a small heater. No combustion, no vent, no roof penetration.
- Direct vent gas fireplaces. A sealed firebox draws outside air and vents exhaust through a pipe within a pipe. It can exit a side wall, which avoids the roof entirely, or go up through the roof when a wall run is impractical. Real flame and useful heat.
- Vent-free gas fireplaces. They burn indoors with no vent, relying on an oxygen depletion sensor. They add moisture and combustion byproducts to the room, manufacturers limit room size, and some jurisdictions restrict them, so check local code first.
- Ethanol fireplaces. Decorative units that burn bioethanol. Modest heat, and the fuel needs careful handling.
What this means for the roof
Every chimney or vent through a roof is one more place to flash and maintain. A wall-vented or ventless unit removes that leak point. Adding a roof-vented fireplace, on the other hand, means a new penetration that must be flashed into the shingles with a storm collar and the manufacturer's listed cap.
If you already have a chimney
Switching to an electric insert or a vent-free unit does not make the old chimney go away. It still needs a cap, a sound crown and good flashing, because an unused chimney leaks just as easily as a working one, and nobody notices until the ceiling stains. If you decide to remove it above the roofline, the opening must be framed, decked, underlaid and shingled, ideally during a roof replacement so the patch blends in. See chimney leaks and crickets and roof flashing explained.